Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/40—Bus networks
  • H04L12/40052—High-speed IEEE 1394 serial bus
  • H04L12/40058—Isochronous transmission
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/40—Bus networks
  • H04L12/40052—High-speed IEEE 1394 serial bus
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/40—Bus networks
  • H04L12/40052—High-speed IEEE 1394 serial bus
  • H04L12/40065—Bandwidth and channel allocation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/40—Bus networks
  • H04L12/40052—High-speed IEEE 1394 serial bus
  • H04L12/40091—Bus bridging

Definitions

• the IEEE 1 394 1 995 standard concerns the configuration and management of one or more serial communication buses. Work is underway to develop an extension of this standard covering networks formed by several buses interconnected by means of assemblies called 'bridges'.
• This extension, called P1 394.1 currently exists in the form of a preliminary draft version 0.03, dated October 1 997.
• a bridge is formed by a couple of devices called portals ('portais' in English), each of the two portals being connected to a bus among two buses to be connected.
• the two gates are connected to each other by a switching fabric ('switching fabric' in English).
• the specification of the bridge switching matrix is outside the scope of P1 394.1 and is left to the implementer.
• FIG. 1 is an example of a wireless bridge between four buses 1394. Each of the buses 1 to 4 is connected to a gate of the bridge, the gates being identified by the letters A to D.
• the bridge of FIG. 1 is an example of incomplete connectivity in the sense that the bridge includes at least one portal that cannot communicate directly with another portal. In the context of the example, there is no direct connection between gates A and D.
• the IEEE 1 394 1 995 standard describes an isochronous transmission process, in which a device ('node') wishing to transmit data pre-books a certain number of isochronous channels.
• a device 'node'
• One of the bus nodes has the function of isochronous resource manager and implements for this purpose two registers, the first indicating the available bandwidth, while the second indicates the isochronous channels available.
• the names of these two registers in the document IEEE 1394 1 995 are respectively 'BANDWIDTH_AVA1LABLE' and 'CHANNEL_AVAILABLE'.
• a node makes a reservation of isochronous resources with the isochronous resource manager by reading the registers and updating their content as necessary.
• the reservation method described in the document IEEE 1 394 1 995 is however not suitable for the bus network connected by a wireless bridge such as that of FIG. 1.
• a bandwidth of width 2X will be required in total: gate A must reserve a first bandwidth of width X for the transmission of A to, for example, C, then a second bandwidth of width X for transmission from C to D.
• the bandwidth depends on the connectivity existing in the network: this type of configuration is not taken into account by the current IEEE 1 394 1 995 standard.
• the subject of the invention is a method of managing resources in a communication network comprising at least two communication buses connected via a wireless transmission bridge, said bridge comprising for each bus a real portal connected to it. bus, each gate being provided with wireless communication means, characterized in that said method comprises the steps of:
• - Figure 2 is a diagram showing a modeling of the bridge of Figure 1 by using virtual buses according to a first embodiment
• - Figure 3 is a diagram showing the real and virtual elements of node A of Figure 2;
• - Figure 4 is a time diagram explaining the exchange of messages between network elements in the context of a resource reservation;
• - Figure 5 shows a modeling of the bridge of Figure 1 by using virtual bi-portal bridges according to a second embodiment;
• FIG. 6 is a diagram showing the real and virtual elements of node A of Figure 5;
• - Figure 7 is a simplification of the modeling according to a first variant of the first embodiment;
• - Figure 8 is an additional simplification of the modeling of Figure 7 according to a second variant of the first embodiment
• - Figure 9a is a diagram representing a modeling of a particular example of link between two nodes, according to the first embodiment
• Figure 9b is a diagram showing a simplification of the modeling of Figure 9a according to a second variant of the first embodiment
• FIG. 10a is a diagram showing a modeling of a particular example of link between two nodes according to the second embodiment
• FIG. 10b is a diagram showing a simplification of the modeling according to a variant of the second embodiment.
• French patent application 98 04982 of April 21, 1 998 filed in the name of THOMSON multimedia and bearing the title 'Synchronization process in a wireless communication network' also relates to a wireless bridge connecting several communication buses, in particular of the IEEE type 1,394 1,995.
• a decomposition of a multi-portal bridge into a given number of bi-portal bridges is carried out by representing a connection between two portals by a virtual bus.
• FIG. 2 Such a modeling in the case of the example of FIG. 1 is given by FIG. 2.
• the dotted lines define the limits of the various nodes acting as a portal.
• node which includes the device itself, as well as the notion of portal, with reference to the primary function of the node.
• This distinction is made to clarify the description which follows.
• a node can simulate, for example in software, virtual elements such as buses and virtual portals.
• the real portal (noted A, B, C or D below) of the node is then put functionally on the same level as the virtual portals, although in reality it is this real portal itself which simulates the virtual elements.
• Each node has a bridge connecting its IEEE 1394 bus to an internal virtual bus.
• This bridge consists of the real portal connected to the IEEE 1 394 bus and a virtual portal connected to the internal virtual bus.
• Each node also has a virtual bridge for each possible wireless link with another node.
• a wireless link is represented by a virtual bus.
• a virtual bridge has two virtual portals, respectively connected to the internal virtual bus of the node and to the virtual bus representing the wireless link.
• Internal virtual buses differ from virtual buses representing wireless links in an important aspect for the reservation of resources: while a virtual bus representing a wireless link has limited bandwidth, this is not the case for the internal bus. .
• the real portal connecting the IEEE bus 1394 is denoted A
• the virtual portal belonging to the same bridge as the real portal is denoted p_A.
• Node A also includes the virtual bus b_A, while the wireless link between node A and node B is represented by the virtual bus b_AB and that the wireless link between node A and node C is represented by b_AC virtual bus.
• the bridge connecting the internal virtual bus b_A to the bus b_AB consists of the portals p_AB.A and p_AB.B, while the bridge connecting the internal virtual bus b_A to the bus b_AC consists of the portals p_AC.A and p AB.A.
• FIG. 3 represents the elements of node A, indicating the separation between real elements and virtual elements.
• Each node A, B, C or D has a physical connection circuit (layer 1 394 PHY), an interfacing circuit (known as a 'LI ⁇ K' circuit), as well as management software for its real portal, managing the registers provided for by standardization work P1 394.1.
• Each node further includes a microprocessor and memory to emulate each of its virtual portals and buses.
• each node A, B, C, D determines thanks to a calibration process the graph of the network, which then allows it to build its virtual topological model in the manner described.
• the information used by a node to establish the graph is obtained using the information communication process of control described in the aforementioned patent application, namely the use of an isochronous frame of the TDMA type.
• Each fixed length frame of the TDMA system in the wireless bridge has a fixed number of control windows, each window being fixedly dedicated to one of the wireless nodes of the bridge.
• a node knows by construction the position of its control window and that of the control windows of the other nodes.
• a node transmits its control information in the control window which is allocated to it, and repeats the information of the control windows of the other nodes. Repeated control information is identified as being repeated by the use of a repetition counter and which is incremented each time the control information is repeated by a node.
• node A When a node A receives control information from a node X in the control window for this node X, then node A deduces that this information comes directly to it from node X. On the other hand, if node A receives the control information of node X in a control window other than that of node X, then this information was repeated and did not reach it directly. Thus, on the one hand, the control information is propagated to all the wireless nodes of the wireless bridge, even if the connectivity is incomplete there, on the other hand each node can determine whether the information which it receives comes directly from 'another knot, or if they have been repeated.
• each time a new node is connected issues a calibration request by inserting it into its control window.
• This request includes a flag for each of the nodes of the wireless network.
• a flag of order j is set to the value 1 if the node sending the request can receive node j, that is to say if there is a direct wireless link.
• This request is then propagated throughout the network using the aforementioned mechanism of the control windows.
• a node detecting a calibration request in a newly occupied control window also generates a calibration request.
• each node At the end of calibration, that is to say once each node has issued its calibration request and it has been transmitted to all the other nodes, each node knows what are the direct wireless links in the wireless bridge. Each node can then proceed to the modeling and the emulation of the buses and portals which concern it, according to the rules which were exposed above. As in the case of the IEEE 1 394 1 995 standard, an isochronous resource manager is designated for each bus, although in the present case these are virtual and not real buses.
• an isochronous resource manager apparatus can be carried out in various ways.
• the two methods described below are given by way of example.
• the element elected manager of isochronous resources on an internal virtual bus is always the virtual portal of the bridge which also includes the real portal of the node. If the node is node X, the virtual portal elected for the internal virtual bus b_X is the portal p_X.
• the election of the isochronous resource manager on a virtual bus representing a wireless link is carried out as follows: (1) Each node A, B, C, D reads from a memory of the other nodes a node identifier called 'EUI64' in document 1 394 1 995. This identifier, unique to each device, has a length of 64 bits.
• Each node determines for each wireless link the largest among the reverse identifier of the node on the other side of the link and its own identifier. If the largest identifier is that of the node on the other side of the link, then the isochronous resource manager of this link is the virtual portal p_XYN, where X designates the node carrying out the determination on its behalf and Y designates the knot on the other side of the link. Otherwise, the portal p_XY.X is designated. Thus, isochronous resource managers are unambiguously appointed. Isochronous resource managers are also designated as the roots of their buses, within the meaning of the IEEE 1394 1995 standard.
• Each isochronous resource manager manages an isochronous channel availability register, which is similar to the 'CHANNEL_AVAILABLE' register described by the document. IEEE 1394 1 995 in section 8.3.2.3.8, and which is similarly accessible. Access to this register, as well as to the wireless bandwidth availability register, will be seen in more detail in connection with FIG. 4.
• the nodes A, B, C and D also elect a manager of the bandwidth of the wireless bridge.
• the isochronous bandwidth manager function is a centralized function at the level of a single device for the entire wireless bridge.
• the isochronous resource manager of each bus manages both the bandwidth availability register and the channel availability register.
• this task is entrusted to the real portal having the largest reverse node identifier.
• each node determines the bandwidth manager by analyzing the identifiers of all the nodes on the network.
• the bandwidth manager manages a wireless bandwidth availability register similar to the bandwidth availability register ('BANDWIDTH_AVAILABLE') defined in section 8.3.2.3.7 of the IEEE 1394 standard, and whose access by the various network elements is also similar.
• the register is initialized to a given value corresponding to the bandwidth available on the wireless network, for example 32 Mbit / s.
• a device connected to one of the real buses 1 to 4 must configure the virtual and real bridges and buses which connect it to the device on the other bus.
• FIG. 4 illustrates the exchanges implemented for reserving isochronous resources on the wireless bridge in order to establish a channel between a decoder 5 (see fig. 1) connected to the IEEE bus 1 394 1 and a decoder 6 connected to the IEEE 1 394 bus 3.
• the configuration process relating to IEEE 1 394 1 and 3 buses is that defined by the IEEE 1 394 1 995 standard and will therefore not be discussed in detail.
• the real portal B was elected bandwidth manager of the wireless bridge.
• the virtual portals p_A, p_AC.A and p_C are respectively the isochronous resource managers of the b_A, b_AC and b_C buses.
• the decoder 5 must make isochronous channel and bandwidth reservations with the corresponding managers of the b_A, b_AC and b_C buses. It must also make a bandwidth reservation with portal B.
• the decoder 5 makes a request to read the content of the isochronous resource availability register of the bus b_A.
• the address of the isochronous resource manager of this bus is composed of the bus address and an offset value for the manager, the value of which is determined by the IEEE 1 394 1 995 standard.
• the request is in fact retrieved by the real portal A, which detects the address of the bus b_A in the request and determines whether the virtual portal p_A is emulated by itself or by another node. Since the portal p_A is well emulated by the real portal A, the latter also emulates the isochronous resource manager of the bus b_A, as well as the availability register of isochronous resources of this bus.
• the content of this register is returned (E2) to the decoder.
• the register identifies those among the 64 channels that are used and those that are free, by the value of one bit per channel.
• the decoder 5 transmits a locking request (E3) which includes the value previously read in the register, as well as a new value to be entered there. This new value indicates, in addition to the channels already identified as reserved in the value read, these two channels that the decoder seeks to reserve.
• the p_A portal compares the old value to that contained in its register of availability of isochronous resources. If this value is identical, the portal enters the new value in the register, and indicates to the decoder that the reservation is effective. It is assumed that this is the case in the example of FIG.
• step E4 If the two values are not identical, then the content of the register has been modified by another device between the time of its reading and of the request for locking by the decoder 5. The content of the register is then not modified. The decoder 5 is informed thereof, and may possibly make a new reservation attempt.
• This register is initialized to the same value as that of the real bus to which the real portal A is connected (for example).
• a bandwidth availability register is also implemented at the level of a virtual bus without bandwidth limitation. In case of bandwidth reservation at such a bus, the content of the register is decremented accordingly. The advantage of emulating this behavior is that it responds to the bus management recommended by the document IEEE 1394 1 995. In the context of this example, the decoder 5 will also attempt to carry out read and lock requests for '' a bandwidth availability register with a bandwidth manager on bus A.
• the decoder 5 reserves the isochronous channels in the same way on the bus b_AB, by sending a read request to the isochronous resource manager of this bus, then a lock request to the portal p_AC.A (steps E5 and E6).
• a device seeking to reserve bandwidth on a virtual bus is addressed to the isochronous resource manager of this virtual bus, as if it were a real bus. .
• the isochronous resource manager knows the address of the bandwidth manager of the wireless bridge, and transmits the request of the initial device by means of this address to the real portal which emulates this function.
• the isochronous resource manager also retrieves the response to the request from the wireless bandwidth manager, and transmits it to the device. For the latter, everything goes so as if he was making a reservation on a real bus.
• the centralization of the bandwidth manager functionality on the wireless bridge is therefore transparent at the reservation level.
• the decoder 5 sends a read request (E7) from the network bandwidth register wirelessly to portal p AC.A, which transmits (E8) the request to portal C. The latter transmits its response (E9) again to portal P_AC.A, which retransmits to decoder 5 (E10).
• E7 a read request
• portal p AC.A which transmits
• portal C the request to portal C.
• portal C the request to portal C.
• the latter transmits its response (E9) again to portal P_AC.A, which retransmits to decoder 5 (E10).
• the process is similar for the lock / write request
• the isochronous channel reservation on the internal virtual bus b_C is carried out with the portal p_C (steps E1 5 to E1 8), in the same way as for the reservation on the internal virtual bus b_A.
• the bandwidth availability register of the wireless bridge is decremented as many times as necessary, as reservations are made.
• the reservation of the isochronous channels carried out on its virtual buses has however no real meaning for the wireless bridge, since a TDMA type mechanism, described in the French patent application already cited, is used by the wireless bridge for transmitting data, a mechanism different from that implemented on an IEEE 1394 bus.
• To an isochronous channel transmitted on a real bus, and to be transmitted over the wireless network corresponds an isochronous wireless channel.
• This isochronous wireless channel corresponds to a constant number of isochronous packets transmitted to each wireless frame. Isochronous packets can be transmitted on the wireless medium in the same format as on an IEEE 1 394 bus.
• the isochronous wireless channel is then defined by the association of the identity of the transmitting wireless node and the channel number used on the real IEEE 1 394 bus on which the wireless transmitter is connected.
• a first variant embodiment of the first example is illustrated by the diagram in FIG. 7.
• This variant makes it possible to simplify the virtual models, and is preferably implemented in the context of stable wireless bridges, that is to say whose Wireless links are not changed or changed at relatively large time intervals. Indeed, in the event of incomplete connectivity, these simplified models require that the connectivity of the wireless bridge be completely recalculated with each topological modification of the bus network.
• link subsets are determined.
• Each wireless node forming part of a link of a subset is in direct connection with any other node of this subset.
• the nodes of a subset are then connected by a virtual bus, which amounts to modeling all the links between the nodes of a subset by a single virtual bus.
• the wireless bridge in the configuration of FIG. 1 gives rise to a new model illustrated by FIG. 7, with the two groups of links AB, AC, BD and BC, BD, CD.
• a second variant of the first embodiment consists in eliminating in the model of the first embodiment the internal virtual bus from a node X which has a single link, to another node Y.
• FIG. 9a illustrates such a case.
• the virtual portals connected to this virtual bus are also eliminated.
• This wireless link is replaced by a bridge formed of the real portal X of node X and a virtual portal p_YXN managed by node Y, these two portals being the remaining portals of the two bridges of the eliminated virtual bus.
• the remaining semi-virtual bridge thus formed is illustrated in FIG. 9b.
• a decomposition of a multi-portal bridge into a given number of bi-portal bridges is carried out by representing a wireless link by a virtual bridge. It is recalled that according to the first embodiment, a wireless link was represented by a bus.
• FIG. 5 describes this modeling.
• the dotted lines in FIG. 5 indicate the limits of each of the nodes A, B, C, D.
• the real and virtual elements located within the limits of a node are managed by the latter.
• FIG. 6 represents the node A and includes the complete references for each of its elements. These references have not all been given in FIG. 5 for reasons of clarity.
• Each node has a bridge connecting its IEEE 1394 bus to an internal virtual bus (b_A, b_B, ).
• This bridge consists of the real portal connected to the IEEE 1394 bus and a virtual portal connected to the internal virtual bus.
• these portals are denoted respectively X and P_X, where X represents one of the nodes A to D.
• Each node X also comprises a virtual portal for each possible wireless link with the other nodes of the wireless network (It is recalled that according to the first example of embodiment, each node included a virtual bridge for each wireless link and not simply a portal).
• These portals are denoted P XY.X, where Y takes in the present case the values B, respectively C, which corresponds to the nodes in direct wireless communication with the node A.
• Two virtual portals corresponding to the same wireless link between two nodes form a virtual bridge (noted L_XY, composed of the portals p XY.X and p_XYN), this virtual bridge representing the wireless link.
• L_XY composed of the portals p XY.X and p_XYN
• a controller for example decoder 5
• it can either configure all the buses and the bridges of the path (as described in the previous example), or send a command to the first bridge on the path, letting it then configure its local bus, and send a command to the next bridge on the path.
• the initial controller is free to select a path (among other possible paths).
• the controller must subcontract the choice of path to the different bridges on the path, each bridge being responsible for finding the next bridge on the path.
• the second approach (command approach) is more indicated in the context of the model based on virtual bridges. Indeed, in this case there is no direct correspondence between a virtual bus and a wireless link, but a direct correspondence between a virtual bridge and a wireless link.
• a controller When a controller wishes to establish an isochronous connection between two nodes of the bus network, he selects from among all the bridges connected by an IEEE 1394 bus to one of the nodes, for example the source node, the bridge which is the most indicated. to support the isochronous connection (for example the closest to the recipient or the least loaded, ). The controller then generates an isochronous connection establishment request command to this bridge, and specifies as parameters the address of the destination node (parameters 'bus_ID' and 'node lD' within the meaning of the document IEEE 1394 1 995), the required bandwidth, and the isochronous channel number used on the local bus (the bus connecting the source node and the first bridge).
• This first bridge makes the necessary reservations on its local virtual bus (channel number, and bandwidth). He then looks for the bridge next most suitable for the requested recipient, and sends him the same command, and so on until the last bridge. If for any reason, a bridge cannot respond to an isochronous connection establishment command (lack of resources on the local bus, etc.), it responds negatively to the command. If resources are available along the way, the order will reach the last bridge, which will respond favorably. Favorable responses are thus relayed step by step to the initiating controller, who interprets this response as an indication that the connection is established.
• the principle specific to wireless communication is that each time a virtual bridge corresponding to a wireless link is crossed, the bandwidth must be reserved with the single isochronous resource manager of the wireless network.
• the decoder 5 reserves a channel number (Y) and the bandwidth (X) on its local IEEE 1394 bus (bus 1).
• the virtual bridge L_AC makes the reservation of bandwidth with the manager of isochronous resources of the wireless network (here portal B) according to the principle previously explained (reading of the contents of the register, then locking). If the reservation has been made, the process continues. Otherwise, the virtual portal L_AC.A responds negatively to portal A, which responds negatively to the decoder 5.
• the portal L_AC.A makes the reservations on the bus b_C in the same way as in point 4, then sends the command to the last bridge (comprising the real portal C and the virtual portal p_C).
• the last bridge makes the channel and bandwidth reservations on the real bus (bus 3) to which the destination node is connected. If reservations have been made (resources have been available), it responds favorably to portal L_AC.A, which responds favorably to portal A, which responds favorably to decoder 5.
• each L_WZ bridge crossed bandwidth reserve with the single manager of the isochronous resources of the wireless network, thus ensuring a coherent management of the wireless resources.
• the internal virtual bus of a node X which has a single wireless link is eliminated, as in the case of the second variant of the first exemplary embodiment, towards another node Y
• the two virtual portals connected to this bus are also eliminated.
• a semi-virtual portal composed of the real portal X and the virtual portal L_XYN.
• Figures 10a and 10b show the same model respectively before and after this simplification.
• the node Y is part of two wireless links. If the node Y was only part of the wireless link XY, then by applying the present simplification, the diagram in FIG. 10b would be reduced to a bridge connecting two real buses and composed of the real portal X and the real portal Y. According to the present variant, this wireless link is replaced by a bridge formed by the real portal X of the node X and a virtual portal p_YXN managed by the node Y. This semi-virtual bridge is illustrated in FIG. 9. Note that the example in Figure 1 does not include a node that is part of only one wireless link.

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• 1998
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